The present invention relates to cargo handling and, in particular, to handling with lift trucks (e.g., fork lifts) using rotation of palletized stacks of cartons or boxes to rotate the stacks of cartons and pallets about 180 degrees around a substantially horizontal axis. Stevedores load and stow in ships many items, including palletized stacks of cartons of frozen animal products. A large volume of animal products such as frozen chicken, turkey, beef, pork, and seafood products are frozen and shipped in boxes or cartons. For example, chicken thighs, legs, or quarters may be shipped in cartons of about 23.5 inches in length by about 16.5 inches in width by about 4 to about 6.25 inches in height (59.7 cm by 41.9 cm by 10.2 to 15.9 cm). Each carton of frozen animal parts may weigh between about 30 and about 45 pounds (14 to 20 kg). A preferred standardized box size can be about 24 inches by about 16 inches (61.0 cm by 40.6 cm) with the height of the box varied to hold the particular products to be shipped. A box of such dimensions containing frozen chicken parts may weigh between about 30 to about 45 pounds (14 to 20 kg). Generally, these cartons are stacked on wooden “two” and/or “four way” pallets in layers. For simplicity, this application refer generally to stacks of cartons of frozen animal products (such as cartons of frozen chicken parts), as other animal products may be similarly handled, or merely to stacks of cartons.
In order to facilitate unitized transportation and storage of stacks of cartons of frozen animal products, the stacks are typically wrapped with a stretchable plastic film (e.g., stretch wrap or shrink wrap) to help reduce sliding of the individual cartons and/or layers of cartons relative to one another and facilitate the handling of the stacks as unitized loads.
A pallet is a platform or open-ended box, usually made of wood, that allows mechanical handling of bulk goods during transport and storage. Although wood is typically used, other materials such as metals, composites, etc., can be used to make pallets. “Two-way” wooden pallets are typically made of three parallel beams (including a center beam and two outer beams). Slats or other surface support members can be nailed, stapled, or otherwise fastened to the upper and lower surfaces of the support beams (slats forming at least the top). “Two-way” pallets can be converted to “four-way” pallets by including openings in the beams along their lower edges and/or removing (or spreading) slats from the bottom to allow insertion of lift truck blades (e.g., forks or tines) parallel to the slats (and generally perpendicular to the beams). “Four-way” pallets can be lifted from any of their four sides—therefore, they are described as “four-way.” However, “two-way” pallets can only be lifted from two directions (e.g., the two directions which are both generally parallel to their beams and generally perpendicular to their slats).
Size restrictions imposed by standard trucks and trailers normally cause the cartons to be stacked on 40 by 48 inch (102 by 122 cm) pallets with five cartons per layer—arranged with layers of two cartons placed on the pallets in an end-to-end relationship beside three cartons placed side to side with their long axes being perpendicular to those of the first two cartons. While the exact sizes of the stacks of cartons may vary depending on the true dimensions of the cartons, stacks of cartons and layers of such stacks will be referred to as having a longer side of 48 inches (122 cm) (called length “L”) and a shorter side of 40 inches (102 cm)(called width “W”). These dimensions are approximate, and may vary depending on box dimensions along with factors such as bulging of the cartons and irregularities in the stacking pattern. In general, however, the cartons have a relatively low aspect ratio (length divided by height). For example, a 4 inch tall by 16 inch long carton would have an aspect ratio of 4 inches by 16 inches or 0.25. A palletload of cartons generally contains between about 10 to 12 layers of cartons. A 12 layer stack of cartons (with 5 cartons per layer) with each carton weighing about 30 pounds (14 kg) would in total weigh about 1800 pounds (818 kg). Two such stacks of cartons would weigh about 3,600 pounds (1,636 kg).
In the frozen animal products industry the general practice includes using pallets having dimensions of 40 by 48 inches (102 by 122 cm), however, 48 by 48 inch pallets (122 by 122 cm) holding five cartons per layer, can also be used. In such cases, the layers can each have two rows of three cartons with the three cartons of each row being in a side-to-side arrangement. Typically, the stacking pattern for either the 40 by 48 or 48 by 48 inch pallets (102 by 122 cm or 122 by 122 cm) may be varied, such as by rotating the stacking pattern from layer to layer. For example, in the 40 by 48 inch (102 by 122 cm) pallets the two end-to-end cartons may be arranged along one of the long edges of the pallet in one layer and rotated 180 degrees in the next layer.
Excessive delays in loading of the stacks of cartons of frozen animal products which result in cartons being left on the dock or in a truck or trailer, can allow the frozen product to begin to thaw, which can result in spoilage, or otherwise render the product unmarketable. Delays in loading may also result in increased condensation of moisture on the cartons which can complicate the handling process. As the industry is seeking to use less wax on the cartons and to utilize paper-coated boxes, the damaging effect of condensation and internal thawing on the boxes is increased and delays should be minimized.
While there have been significant advances in the methods of loading and unloading of ships or vessels, the loading of stacks of cartons of frozen animal products has proved difficult due to many problems associated with the handling of stacks of frozen animal products. As a result, the loading of stacks of frozen animal products onto ships is currently carried out by methods involving high costs, significant expenditures of labor, and which include various bottlenecks slowing down the process—resulting in excessively large loading times, along with product damage, degradation, and/or spoilage.
Space on refrigerated vessels is at a premium. Stowing the pallets with the stacks of cartons of frozen animal products takes valuable storage space away from the possible stowage of additional cartons. Accordingly, the practice has been to stow the cartons without the pallets. Removing the pallets has been done manually, e.g., by hand restacking the cartons without the pallets. Additionally, removing the pallets has been done mechanically, e.g., by pushing the stacks of cartons off of the pallets. However, these prior art methods of depalletizing the palletized stacks of cartons have various disadvantages.
When it is time to load a ship with the cartons, lift trucks can be used to remove the palletloads of stacks of cartons frozen animal products from the cold storage warehouse, and place them inside dry van trucks or truck trailers for transportation to the dock where the ship is waiting to be loaded. The trucks or truck trailers are typically uninsulated and unrefrigerated, and thus can provide a deleterious environment to the stacks of frozen animal products if they are not soon loaded into the refrigerated ship. At the dock, the cartons can be removed from the truck trailer by lift trucks and placed on the dock. Alternatively, if the cold storage warehouse is sufficiently near to the dock, the lift trucks may transport the palletized stacks of cartons directly to the dock.
Hand loading has been used for many years. The palletized stacks of cartons can be lifted or hoisted into the ship's hold using lifting robots, carriers, slings, lifting platforms, lift cages, flying forks, or the like. In the hold, lift trucks can move the palletized stacks of cartons and transport the palletized stacks closed to their ultimate stowage location. Stevedores can then manually (i.e., by hand) unstack the individual cartons from the pallets and restack the cartons without pallets for shipping. The empty pallets can then be removed from the hold. Manual unloading can be slowed by the time it takes to manually unstack and restack the individual cartons along with delays in returning pallets shipside.
One method proposed to decrease loading times and increase loading efficiency (compared to manual unstacking and restacking) is described in U.S. Pat. No. 6,622,854 (for a “Method and Apparatus for Loading Stacks of Cartons of Frozen Animal Products Onto Vessels Using a Carrier”), which patent is incorporated herein by reference. In its abstract this patent describes using “[a] method for rapid loading of stacks of cartons aboard vessels is provided which may include sliding the stacks of cartons from a pallet onto a carrier having fork channels receiving the blades of a load push lift truck, lifting the carrier into the hold of a vessel, removing the stacks of cartons from the carrier using a second load push lift truck and stowing the stack of cartons in a stowage location using the second load push lift truck.” One of the disadvantages of the method described in the '854 patent is the damage to the cartons (and frozen animal products) caused by sliding the stacks of cartons off of their pallets and onto the carrier. Even where the cartons are pushed in the direction of the supporting pallet slats, damage to the cartons can occur by discontinuities in the slats (e.g., nails, splintered portions, and/or misaligned slats). Damage to the cartons both slows down the overall loading process and typically is charged to the stevedore—both being undesirable. Another of the disadvantages of the method described in the '854 patent is the time it takes to slide the stacks of cartons off of pallets. During the process of sliding, the load push lift truck is necessarily immobile (and cannot ambulate from one place to another, e.g., traveling towards the carrier to deposit the depalletized stack of cartons), also slowing down the overall loading process and efficiency. Another disadvantages of the method described in the '854 patent, is the requirement that two stacks of cartons being simultaneously slid onto the carrier have their lengths (i.e., their 48 inch sides) parallel to and co-linear with each other. This necessarily increases the overall length of the carrier being used to lift the stacks (the dimensions of the two stacks of cartons 40 inches by 96 inches). This is required because the stacks are pushed in the direction of the upper slats of the four way pallets (i.e., such slats are parallel to the 40 inch sides of the stacks and perpendicular to the 48 inch sides of the stacks).
It would be advantageous to develop a method of depalletizing the stacks of cartons where the stacks are not required to be slid off of the pallets.
It would be advantageous to develop a method of depalletizing where the stacks can be both rotated and simultaneously moved to the area where they will be hoisted to the ship.
It would be advantageous to develop a method of depalletizing two stacks of cartons where the 40 inch sides of each stack are parallel to and co-linear with each other making the dimension of the two stacks 48 inches by 80 inches taking up less longitudinal length in the hold and allowing the load push lift trucks to have more room to work around the hold.
Many of the ships transporting cartons of frozen animal products internationally are older vessels having ship's gear (e.g., union purchases and/or cranes) with a three-ton (metric) rated capacities. This permits the ship's gear to lift up to three stacks of cartons at a time, depending on the weight of the stacks, along with the weight of the ship's gear used to lift the stacks. However, other ships may have cranes with capacities of five or more tons. Because of structural concerns, the weight of a lifting robot or carrier used to hoist two stacks of cartons can approach one ton. Accordingly, with three-ton ship's cranes or union purchases, generally only two stacks of cartons at a time can be lifted into the hold of the ship. In some cases loading docks may include dock cranes or mobile cranes which can be used to hoist or lift loads into the ships allowing for the hoisting of heavier loads.
Incorporated herein by reference is published European Patent Application number 86202117.7, published as EPO publication number EP0224966 “Method for loading piece goods, supplied on pallets, into a hold, particularly a hold of a vessel.”
While certain novel features of this invention shown and described below are pointed out in the annexed claims, the invention is not intended to be limited to the details specified, since a person of ordinary skill in the relevant art will understand that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation may be made without departing in any way from the spirit of the present invention. No feature of the invention is critical or essential unless it is expressly stated as being “critical” or “essential.”